关键词: 低阶煤, 微波, 介电响应, 微波能利用效率

Abstract: The dielectric response or dielectric loss of low-rank coal determines the feasibility and economic benefit of microwave heating. According to the propagation rule of microwave in dielectric, the quantitative relationship between microwave energy utilization efficiency and complex relative dielectric constant was derived, and two important parameters describing microwave energy utilization efficiency, microwave absorption coefficient and the average power density of dielectric loss, were derived. In this paper, the influence of coal properties and coal species on microwave dielectric response was studied based on four kinds of low-rank coal. The relationship between dielectric response parameters and microwave heating characteristics was also discussed. The results show that, the microwave absorption coefficient and the average power density of dielectric loss were only affected by their properties under the condition that microwave frequency was fixed and temperature changed little. Moisture and pyrite could help to promote the dielectric response of low-rank coal to microwave, and the particle size which was equal to or less than penetration depth had little effect on microwave dielectric response. The microwave radiation time in the low temperature stage was almost 50% of the total radiation time, that was, 50% of the total energy consumption. The dielectric response parameters of low-rank coal to microwave could reasonably explain the heating characteristics at this stage. Therefore, the dielectric response parameters had important guiding significance for the selection of coal, pyrolysis technology and equipment.